The present invention relates to a specifically formulated color ink composition for use in ink jet printing applications.
The market for color hard copy devices is a rapidly growing one, being driven by increasingly large numbers of color displays in use in various types of computing systems. In this regard, ink jet printing has been successfully applied to color graphics applications since ink jets are capable of making color hard copies having excellent image quality.
Color inks for use in ink jet printers are typically formulated to a fairly specific set of color and physical properties. To this end, the use generally of water-soluble dyes in conjunction with a solvent, such as water, and a water-miscible organic compound such as N-alkanolamines, have been employed. See Japanese No. 61036380 (abstract), Japanese No. 81147750 (abstract), German No. 3445225 (abstract), Japanese No. 6105766 (abstract), Japanese No. 61085886 (abstract). Other patents relating to ink jet printing produce aqueous magenta inks by dissolving two water-soluble red dyes in water. In Japanese No. 60149676 (abstract), C.I. Reactive Red 66 is one of the dyes employed. In Japanese No. 61179275 (abstract), Acid Red 92 is used in conjunction with at least one dye selected from Acid Red 35, Acid Red 37, Acid Red 249, Acid Red 254, Acid Red 289, Direct Red 9, and Direct Red 227. Regarding aqueous ink compositions using various blue (cyan) dyes, Direct 86 has been employed in Japanese No. 60092369 (abstract), Japanese No. 59051959 (abstract), Japanese No. 60199078 (abstract), and Japanese No. 60197778 (abstract). Finally, Japanese No. 59093765 (abstract) and Japanese No. 58208357 (abstract) describe the use of various black dyes in ink compositions for jet printing purposes.
There are situations in which the hard copy produced by the color ink jet printer should closely match the corresponding color image displayed on a CRT screen. One method of matching hard copy colors to video display colors is described in U.S. Pat. No. 4,670,780 to McManus et al. For a video display, McManus et al. notes that color is produced by adding light emissions from the red, green and blue phosphors, while for a hard copy device, color is produced by subtracting light via the inks used to print the image on a record medium. The result is that, typically, the video display red is not the same as the hard copy red. In FIG. 1 of the McManus et al. patent, the color gamuts of a particular video display and a particular ink and paper system are shown. In the method of McManus et al., a color transformation algorithm is provided for matching video display color the hard copy color, taking into account both the limitations of video color and of the imperfect character of the colorants in the inks used. Even with the McManus et al. method, it is still highly desirable to provide ink compositions that are specifically formulated to provide an improved visual match with a video color image as actually displayed on a CRT, particularly at lower intensity settings.
Therefore, a need exists for improved ink compositions for use in an ink jet color printer to produce a color hard copy that more satisfactorily reproduces the color image displayed on the CRT associated with that color printer.